The battery itself is not charged, its two poles have positive and negative charge, the positive and negative charge generated by the voltage (electric current is the role of the electric charge in the direction of the movement of the electricity), charge is widely present in the conductor of the conductive ions, to generate electricity only need to add voltage.

The charge is released when the battery is connected to the conductor in order to generate an electric current, and when the charge is dispersed, the dry battery is called a power supply, and a device that turns alternating current into a DC is called a rectifier power supply through a transformer and a rectifier. An electronic device that provides a signal is called a signal source.

LED power supply is constant current source, general switching power supply is constant voltage source.

Working principle: LED power supply has 2 requirements, the first requirement output voltage >led of the conduction voltage, followed by the requirements of the operating current stability, and can not be greater than the LED rated current. When the operating current of the LED exceeds the rated current, the LED will soon appear aging damaged. Therefore, the LED power supply must have constant current function.

In the design of LED switching power supply, first determine the LED current, and then according to the use of the number of lamp beads in tandem to determine the power supply voltage. The current is used as the main working parameter and the voltage is the auxiliary parameter.